Rotary guiding tool and transmission device

ABSTRACT

The present invention provides a rotary guiding tool, comprising: a power unit having an output shaft capable of outputting a torque and an offset driving portion capable of outputting a radial force and/or an axial force; a transmission shaft connected with the output shaft; a support shaft connected with the transmission shaft through a rotation structure, wherein a rotation axis of the rotation structure is perpendicular to an axis of the output shaft, the support shaft has an inner wall defining an accommodating cavity and a forward end and a rearward end formed at both ends of the accommodating cavity, a rotation center of the rotation structure is located in the accommodating cavity, and the rearward end of the support shaft is capable of being driven by the radial force output by the offset driving portion; and a drill bit having a drill bit tail end, wherein the drill bit and the forward end of the support shaft are connected to the drill bit tail end. According to the present invention, the rotary guiding tool may improve the whipstocking ability of the drilling tool, and reduce the energy consumption of driving the drilling tool.

TECHNICAL FIELD

The invention relates to a rotary guiding tool and an equipment device for improving the whipstocking ability of the rotary guiding drilling equipment, and belongs to the field of oil drilling.

BACKGROUND TECHNOLOGY

At present, rotary guiding drilling technology is a breakthrough and strategically significant technology among various advanced drilling technologies and processes developed at home and abroad. Since its appearance in the 1990s, it has set off a revolution in directional drilling technology.

Before the advent of rotary guiding drilling technology, a sliding guiding drilling system driven by a mud motor was used to implement guiding drilling. The sliding guiding drilling system does not rotate during the guiding drilling process, but slides along the axis of the well wall and uses the sliding guiding tool to change the inclination and azimuth angles of the well bore, thereby controlling the well bore trajectory. The problems of the sliding guiding drilling system include the difficulty in sliding, the need of maintaining orientation, the poor cleanliness of the bore hole, and the low drilling speed, which may cause buckling and self-locking and the like. The existence of these problems affects the progress of drilling and the normal operation of the drilling equipment.

The rotary guiding drilling system maintains the rotary drilling in a direction of the bore hole during the drilling process. Compared with the sliding guiding drilling system, it has the advantages of low friction and torsion resistance, high drilling speed, low cost, short well construction period, and smooth well trajectory which is easy to control, and extended horizontal section length.

There are two commonly used rotary guiding technologies, one is a directional guidance and the other is a push-oriented guidance. The Chinese authorized patent CN104619944B obtained by the American company Halliburton discloses a directional guiding tool, which provides modular actuators, guiding tools and rotary guiding drilling systems, the modular actuator includes a barrel portion, and the modular actuator is configured to be coupled to an outer circumference of the outer casing. The accumulator is housed in the barrel portion, and a hydraulically actuated actuator is slidably disposed within the barrel portion, the actuator is moveable between an activated position and an inactive position such that the actuator piston selectively squeezes the ramped surface of the drive shaft to change the direction of the drill string.

The U.S. patent application US20140209389A1 discloses a rotary guiding tool, which comprises a non-rotating sleeve, a rotating shaft comprising a deflectable unit, the deflection unit being deflected by controlling the circumferential position of the eccentric bushing, thereby adjusting the drilling direction of the drill bit.

Another type of rotary guiding technique, namely push-oriented rotary guidance technology, is disclosed in US Patent Application No. US20170107762A1, it includes a pushing member disposed around the drill pipe and a hydraulic drive system for driving the pushing member, and the hydraulic drive system selectively drives the pushing member to move between the abutment position and the non-push position, in the abutment position, the pushing member can push against the wall of the well in a slapping way to generate guiding force and change the direction of the drilling hole. The push-oriented rotary guidance system needs to apply a guiding force to the entire drill tool assembly in the actual operation process, and since the rigidity of the drill tool assembly is relatively large, the whipstocking ability of the push-oriented rotary guidance system is limited.

It should be noted that the above content belongs to the technical cognition category of the inventors, and does not necessarily constitute the prior art.

SUMMARY

In order to solve the above problems, the present invention provides a rotary guiding tool, which is characterized in that it comprises

-   -   a power unit having an output shaft capable of outputting a         torque and an offset driving portion capable of outputting a         radial force and/or an axial force;     -   a transmission shaft connected with the output shaft;     -   a support shaft connected with the transmission shaft through a         rotation structure, a rotation axis of the rotation structure is         perpendicular to an axis of the output shaft; the support shaft         has         -   an inner wall defining an accommodating cavity, and a             forward end and a rearward end formed at both ends of the             accommodating cavity; a rotation center of the rotation             structure is located in the accommodating cavity; the             rearward end of the support shaft is capable of being driven             by the radial force output by the offset driving portion;             and     -   a drill bit having a drill bit tail end, the drill bit and the         forward end of the support shaft are connected to the drill bit         tail end.

The driving torque of the power unit is transmitted to the drill bit through the above-mentioned rotary guiding tool, wherein the support shaft is sleeved on the outside of the transmission shaft, and the transmission shaft and the support shaft partially overlap in the axial direction, thereby making the rotation structure connecting the transmission shaft and the support shaft can be as close as possible to the drill bit. When performing the whipstocking operation, the radius of curvature of the transmission device connecting the power unit and the drill bit is as small as possible. When the radial movement of the same amplitude occurs under the driving of the radial load, the smaller the radius of curvature, the larger the bending angle, which can improve the efficiency of the change of inclination angle and azimuth angle to improve the whipstocking ability of the rotary guiding tool.

In addition, the support shaft constitutes the external structure of the aforementioned transmission device, and the power unit applies a lateral force or radial force to an upper support shaft through a force application structure. Under the action of the axial force or the radial force, the support shaft will generate an offset around the rotation structure, so that the center line of the transmission shaft and the combined axis of the drilling tool and the support shaft will generate an offset angle. Meanwhile, under the action of the fulcrum, the force borne by the support shaft will be directly transmitted to the drill bit, and finally the entire rotary guiding tool will produce a whipstocking rate in the specified direction. As mentioned above, under the driving whipstocking force applied by the power unit, the force-receiving part is only the support shaft instead of the entire drill tool assembly (including drill collars and other structures), which can shorten the arm of resistance caused by dead weight load and reaction load, thus this type of structure can reduce unnecessary energy consumption and reduce the power consumption of the driving system including the power unit.

In addition, the axial nesting overlap of the transmission shaft and the support shaft and the change of the force position of the driving force can also reduce the possibility of self-locking. In the whipstocking operation, the direction of the bore hole will be changed according to needs. At this time, the three-point circular is used to make the drilling tool bend. When the direction of the bore hole changes greatly, the transmission shaft and the support shaft may be stuck in the bore hole of the different sections and self-lock. This also means that the use of the three-point circular bending drive method requires gradually changing the inclination angle and azimuth angle to limit the whipstocking ability of the drilling tool. However, in the solution of the present invention, the driving force for changing the direction of the drill tool is directly applied to the support shaft connected to the drill bit, and the three-point circular method is no longer used. At the same time, the distance between the rotation node and the drill bit is shortened, which is mainly beneficial to shorten the length of the support shaft to reduce the possibility of self-locking.

In a preferred embodiment, the rotation structure comprises a rotation joint that forms a spherical pair with the support shaft, and a flexible member that passes through the rotation joint and is connected with the support shaft.

The implementation of the rotation structure preferably adopts a flexible hinge structure. In order to allow the transmission shaft and the support shaft to rotate relative to each other to form a substantial bend, the spherical pair provides a rotating track, and the flexible member is bent and deformed to achieve a flexible hinge. The flexible member itself also has the function of storing elastic potential energy and gradually driving the rotation structure back straight.

In a preferred embodiment, the rotation joint comprises a first protrusion proximal to the forward end of the support shaft and having a first truncated spherical surface portion, the support shaft has a first groove, and the first groove and the first protrusion cooperate at the first truncated spherical surface portion to form a spherical pair.

The spherical pair is distributed at least at an end of the transmission shaft proximal to the forward end of the support shaft, the transmission shaft extends into the accommodating cavity formed by the support shaft, and the first groove formed in the accommodating cavity first stops the movement tendency of the transmission shaft approaching the forward end. In addition, it also provides a rotating contact surface, no matter whether the driving force is axial force or radial force, after pushing the support shaft, it will drive the support shaft to rotate relative to the transmission shaft based on the spherical pair. The contact surface of the spherical pair here will bear a certain load, and the area formed by the spherical pair will be a truncated spherical surface. The angle range of the truncated spherical portion will be greater than an allowable maximum rotation angle. The maximum rotation angle is defined as a maximum relative rotation angle at which the transmission shaft and the support shaft are allowed.

The spherical pair also plays a role of supporting. When the drill bit bears the geological reaction load of the drilling layer, the spherical pair helps to stably support the transmission shaft in the support shaft.

In a preferred embodiment, a surface hardness of the first groove is greater than a surface hardness of the first protrusion.

The surface hardness of the first groove is greater than that of the first protrusion, which is represented by a wear-resistant material, for example, a wear-resistant cast iron material is used or a surface-treated wear-resistant layer is formed on the surface of the first groove. One implementation is to provide a detachable wear-resistant sleeve in the accommodating cavity of the support shaft, and the first groove is formed on the wear-resistant sleeve. The formation position of the spherical pair will be a position where the load is concentrated, and the position is also the wear-prone position. It is set as a detachable structure, which is convenient for maintenance and replacement.

In a preferred embodiment, the rotation structure further comprises a pair of connection keys arranged with a central axis of rotation of the transmission shaft as a symmetrical axis, the pair of connection keys are mounted on the rotation joint, and the support shaft is formed with a key slot cooperating with the connection keys;

-   -   the connection key has a second protrusion, and a surface of the         second protrusion is of a truncated cylindrical shape with a         rotation axis of the rotation structure as a central axis.

In order to reliably transmit the torque, the support shaft and the transmission shaft are set as the key connection, and in order to achieve relative rotation, the top of the connection key is set as a cylindrical surface to support the top of the connection keys without interference with the key slot during rotation.

In a preferred embodiment, the rotation joint further comprises a third protrusion formed at an end, distal from the forward end of the support shaft, of the connection key; the third protrusion has a second truncated spherical surface portion that is concentric with the first truncated spherical surface portion;

-   -   the support shaft has a third groove, and the third groove and         the third protrusion cooperate at a second cross section         spherical surface portion to form a spherical pair.

In a more perfect rotation structure, a third protrusion opposite to the first protrusion is provided, that is, a third protrusion distal from the forward end of the support shaft relative to the first protrusion is provided, and spherical supports are provided at opposite ends. While stopping the tendency of the transmission shaft to move away from the forward end of the support shaft, the rotation joint is limited by the first groove and the third groove jointly, and the rotation joint is stably supported.

In a preferred implementation, the third groove is formed in a blocking structure provided in the accommodating cavity installed on the support shaft, which facilitates the non-return member and the transmission shaft to extend into the accommodating cavity of the support shaft, and the movement tendency close to the front end of the support shaft is stopped by the internal structure of the support shaft, and the movement tendency out of the support will be stopped by the blocking structure.

In a preferred embodiment, an end of the flexible member is mounted on a fixed portion of the support shaft, and the other end of the flexible member is supported by a support portion of the transmission shaft; the rotation center of the rotation structure is located between the fixed portion and the support portion.

The flexible member is arranged to pass through the rotation center of the rotation structure, that is, the bending deformation structure and the rotation structure form a positional relationship that partially overlaps, which is also a further optimized way to shorten the overall radius of curvature of the bending structure. In addition, the flexible member preferably is a flexible sleeve structure, and has a hollow channel and the openings at both ends of the channel. The flexible member passes through the center of rotation. An opening at one end connected to the support shaft allows the mud passing through the drill bit to flow in, enter the hollow channel, and then flow out from the opening at the end of the transmission shaft to flow into the power unit. The mud removal at the rear end is consistent with the traditional guiding drill method and principle. That is, in this preferred manner, the mud passage through the rotation structure is provided by the flexible sleeve, and the central axis of the flexible sleeve preferably coincides with or nearly coincides with the central axis of the transmission shaft.

In a preferred embodiment, the rotary guiding tool further comprises an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.

As the buffer and lubrication of the rotation structure, a medium cavity is formed between the support shaft and the transmission shaft to flush the lubricating medium such as hydraulic oil. The lubrication is mainly for the rotating pair and the spherical pair formed on each contact surface, while the filled medium can also play a role of buffering the impact of the load. For example, the pressure balance portion has an elastic sleeve-shaped member, with the two ends respectively connected to the transmission shaft and the support shaft, and a medium extension cavity communicating with the medium cavity is formed between the sleeve-shaped member and the transmission shaft. When the transmission shaft and the support shaft rotate relative to each other, the medium in the medium extension cavity is compressed, and one side of the sleeve-shaped member will also be compressed. Both of these two kinds of compression will generate energy accumulation, which will help to maintain the overall pressure balance of the rotation structure. A typical sleeve-shaped member is a bellows, and a heat-resistant rubber sleeve similar in shape to the bellows can also be used.

In a preferred embodiment, a shortest distance between the rotation center and the drill bit tail end is not greater than 3.5 times of a maximum radial dimension of the support shaft.

As an advantageous design, the support shaft for mounting the drill bit is designed to be shorter. By referring to the radial size of the support shaft, shortening the support shaft, especially the size from the rotation center of the support shaft to the drill bit installation position, is more conducive to taking advantage of the rotation structure described in the technical solution of the present invention, that is, reducing the radius of curvature, improving the whipstocking ability and reducing the wear of the drill tool.

Meanwhile, in the present invention, the transmission device formed by the transmission shaft and the support shaft will also be explained as an independent technical solution for protection. The technical solution is as follows:

A transmission device, separately connected to:

-   -   a power unit having an output shaft capable of outputting a         torque and an offset driving portion capable of outputting a         radial force;     -   a drill bit having a drill bit tail end;     -   wherein, the transmission device comprises:     -   a transmission shaft coaxially connected with the output shaft;     -   a support shaft coaxially connected with the transmission shaft         through a rotation structure, wherein a rotation axis of the         rotation structure is perpendicular to an axis of the output         shaft; the support shaft has     -   an accommodating cavity and a forward end and a rearward end         formed at both ends of the accommodating cavity; a rotation         center of the rotation structure is located in the accommodating         cavity; the rearward end of the support shaft is capable of         being driven by the radial force output by the offset driving         portion; and the forward end and the drill bit are coaxially         connected to the drill bit tail end.

The advantages of the transmission device will be embodied through the use of the aforementioned rotary guiding tool, and thus will not be repeated here.

BRIEF DESCRIPTION OF DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of this invention. The schematic embodiments of this invention and their descriptions are used to interpret this invention and do not constitute an undue limitation of this invention. In the drawings:

FIG. 1 depicts a structural composition schematic diagram of a rotary guiding tool according to an embodiment of the invention.

FIG. 2 depicts a structural composition schematic diagram of the transmission device of the rotary guiding tool according to an embodiment of the invention.

FIG. 3 depicts a structural schematic diagram of the transmission shaft of the rotary guiding tool according to an embodiment of the invention.

DETAIL DESCRIPTIONS OF EMBODIMENTS

In order to explain the overall concept of the present invention more clearly, the following detailed description is illustrated by way of example with reference to the attached drawings.

It should be noted that in the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

In addition, in the descriptions of the present invention, it should be understood that the terms, such as “center”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “axial”, “radial”, “circumferential”, indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

In the present invention, unless otherwise clearly specified and limited, the terms, such as “installation”, “interconnection”, “connection”, “fixed” should be understood in a broad sense, for example, the connection may be a fixed connection, a detachable connection or an integrated connection; and the connection may be a direct connection or an indirect connection through an intermediate medium; and the connection may be the communication between two elements or the interaction between two elements. However, the indication of direct connection means that the connected two main bodies do not build a connection relationship through a transition structure, but are only connected through a connection structure to form a whole. The ordinary artisans concerned may understand the specific meaning of terms in this disclosure according to specific circumstance.

In the present invention, unless otherwise specified and defined, the first feature is “on” or “under” the second feature means that the first and second features may be in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, descriptions with reference to the terms, such as “one embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples”, mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In the present specification, the schematic representation of the above terms does not necessarily mean the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

As shown in FIG. 1, in an embodiment of the present invention, a structural schematic diagram of a down hole drilling tool assembly is described, wherein a rotary guiding tool comprises a drill bit 110, a transmission device 120 and a power unit 130. In addition, the assembly also includes an MWD unit 140 that cooperates with the rotary guiding tool.

For each part of the structure, the drill bit 110 is used for drilling, cutting and destroying the rock formation, and plays the role of rock breaking, and is directly connected with the transmission device 120; the power unit assembly 130 provides a driving force for the transmission device 120, and the driving force can be a radial or axial force and also provides a torque that drives the drill to rotate. The MWD unit 140 is a conventionally configured monitoring device that can measure and monitor well bore trajectory parameters and rotating guiding tool's working progress in a real time, and is equipped with a mud pulse generator or electromagnetic wave transmission unit to transmit the down hole useful information to the surface operating system.

FIG. 2 is a schematic diagram of the structural assembly of the transmission device 120. The transmission device comprises a transmission shaft and the support shaft, and the transmission shaft extends into the support shaft and the transmission shaft and the support shaft are connected by a rotation joint, which can transmit torque between the transmission shaft and the support shaft, and the transmission shaft and the support shaft can rotate relatively through the rotation joint, to change the direction of the drill bit to adjust the inclination and azimuth angles.

As shown in the figure, the support shaft includes an upper support shaft 1211 and a lower support shaft 1201. The lower support shaft 1201 is connected to the drill bit. The transmission shaft 1202 and the connection key 1203 are the main power transmission components, the shapes of which are shown in FIG. 3. The connection key 1203 will cooperate with the key slot formed in the lower support shaft 1201 and having the accommodating cavity to transmit torque, and the connection key will also cooperate with the key slot to form a rotating pair. As shown in the figure, the two pairs of connection keys are connected to the rotation joint of the front section of the transmission shaft through a hole column structure. When the lower support shaft rotates relative to one of the pairs of connection keys, a center shaft of the other pair of connection keys with a hole column connection structure is used as the rotation shaft. The center of the hole column connection of each connection key meets the rotation center of the rotation joint.

The transmission shaft 1202 is fixedly connected with the power unit through a threaded structure, so that it can withstand the torque and driving force provided by the power unit.

Jacking member 1204 and the flexible wear-resistant sleeve 1205 are used to seal and isolate the mud passage in the device from the outer annular mud passage. Meanwhile, the jacking member is fixedly connected to the lower support shaft, which can be regarded as a part of the support shaft, that is, one end of the flexible wear-resistant sleeve is fixedly connected to the support shaft. The other end of the flexible wear-resistant sleeve is supported on the inner hole of the transmission shaft and sealed by a sealing structure.

There is a spherical pair structure between the wear-resistant sleeve 1206 and the transmission shaft 1202, thereby forming a universal transmission node. The structure of the spherical pair is shown in the figure, including a front-end spherical pair and a rear-end spherical pair. Specifically, the rotation joint includes a first protrusion with a first truncated spherical surface portion proximal to the forward end of the support shaft. The support shaft has a first groove, and the first groove and the first protrusion cooperate at the first truncated spherical surface portion to form the front-end spherical pair. The rotation joint further includes a third protrusion formed at one end of the forward end of the connecting key distal from the support shaft. The third protrusion has a second truncated spherical surface portion that is concentric with the first truncated spherical surface portion. The support shaft has a third groove, and the third groove and the third protrusion cooperate at the second truncated spherical surface portion to form the rear-end spherical pair.

The anti-dropping member 1207 is mainly used to prevent the transmission device from separating from the drilling tool assembly during the lifting process of the rotary guiding tool. Specifically, it is to prevent the transmission shaft from separating from the support shaft.

The rotation joint is immersed in the closed hydraulic oil filled in the medium cavity. The hydraulic oil must be vacuumed before working. The oil circuit system has a sleeve-shaped pressure balance member 1208 with the two ends connected to the transmission shaft and the support shaft, respectively, which may be a high temperature resistant rubber member, but also can be a metal bellows or other type of balance structure. It can adaptively balance the external mud pressure to automatically adapt to the underground high temperature and high pressure environment.

The oil filling plugs 1209 and 1212 are used to seal the oil filling ports of the medium cavity containing the hydraulic oil, and the oil filling plugs 1209 and 1212 are removed after the tool is assembled. Then the external vacuum oil filling device is connected to complete the oil filling operation. The sealing members 1213 and 1214 are high-temperature static sealing structures, such as O-rings, to achieve a sealing function.

In the actual working process, for the upper support shaft 1211 and the power unit, the power unit applies a force to the upper support shaft 1211 through a suitable force application structure. This force can be a radial force or an axial force. The bias around the rotation structure is generated under the action of the force, so that a center line of the rotary guiding tool and an axis of the drilling tool assembly generate an offset angle. Meanwhile, under the action of the fulcrum, the force borne by the upper support shaft will be directly transmitted to the drill bit part through the lower support shaft, and finally the entire drill tool assembly will generate a whipstocking rate in a specified direction. Since the force-bearing part is only the transmission device, rather than the entire drill tool assembly, this type of rotary guiding structure reduces unnecessary energy consumption, and meanwhile the whipstocking ability will be improved.

The parts of the present invention that are not described in detail belong to the common knowledge of those skilled in the art. 

1-10. (canceled)
 11. A rotary guiding tool, wherein, comprising: a power unit having an output shaft capable of outputting a torque and an offset driving portion capable of outputting a radial force and/or an axial force; a transmission shaft connected with the output shaft; a support shaft connected with the transmission shaft through a rotation structure, a rotation axis of the rotation structure is perpendicular to an axis of the output shaft, the support shaft has an inner wall defining an accommodating cavity, and a forward end and a rearward end formed at both ends of the accommodating cavity, a rotation center of the rotation structure is located in the accommodating cavity, and the rearward end of the support shaft is capable of being driven by the radial force output by the offset driving portion; and a drill bit having a drill bit tail end, the drill bit and the forward end of the support shaft are connected to the drill bit tail end.
 12. The rotary guiding tool of claim 11, wherein, the rotation structure comprises a rotation joint that forms a spherical pair with the support shaft, and a flexible member that passes through the rotation joint and is connected with the support shaft.
 13. The rotary guiding tool of claim 12, wherein, the rotation joint comprises a first protrusion proximal to the forward end of the support shaft and having a first truncated spherical surface portion, the support shaft has a first groove, and the first groove and the first protrusion cooperate at the first truncated spherical surface portion to form a spherical pair.
 14. The rotary guiding tool of claim 13, wherein, a surface hardness of the first groove is greater than a surface hardness of the first protrusion.
 15. The rotary guiding tool of claim 13, wherein, the rotation joint further comprises a pair of connection keys arranged with a central axis of rotation of the transmission shaft as a symmetrical axis, the pair of connection keys are mounted on the rotation joint, and the support shaft is formed with a key slot cooperating with the connection keys; the connection key has a second protrusion, and a surface of the second protrusion is of a truncated cylindrical shape with a rotation axis of the rotation structure as a central axis.
 16. The rotary guiding tool of claim 13, wherein, the rotation joint further comprises a third protrusion formed at an end, distal from the forward end of the support shaft, of the connection key, the third protrusion has a second truncated spherical surface portion that is concentric with the first truncated spherical surface portion, the support shaft has a third groove, and the third groove and the third protrusion cooperate at a second cross section spherical surface portion to form a spherical pair.
 17. The rotary guiding tool of claim 14, wherein, the rotation joint further comprises a third protrusion formed at an end, distal from the forward end of the support shaft, of the connection key, the third protrusion has a second truncated spherical surface portion that is concentric with the first truncated spherical surface portion, the support shaft has a third groove, and the third groove and the third protrusion cooperate at a second cross section spherical surface portion to form a spherical pair.
 18. The rotary guiding tool of claim 15, wherein, the rotation joint further comprises a third protrusion formed at an end, distal from the forward end of the support shaft, of the connection key, the third protrusion has a second truncated spherical surface portion that is concentric with the first truncated spherical surface portion, the support shaft has a third groove, and the third groove and the third protrusion cooperate at a second cross section spherical surface portion to form a spherical pair.
 19. The rotary guiding tool of claim 12, wherein, an end of the flexible member is mounted on a fixed portion of the support shaft, the other end of the flexible member is supported by a support portion of the transmission shaft, and the rotation center of the rotation structure is located between the fixed portion and the support portion.
 20. The rotary guiding tool of claim 13, wherein, an end of the flexible member is mounted on a fixed portion of the support shaft, the other end of the flexible member is supported by a support portion of the transmission shaft, and the rotation center of the rotation structure is located between the fixed portion and the support portion.
 21. The rotary guiding tool of claim 14, wherein, an end of the flexible member is mounted on a fixed portion of the support shaft, the other end of the flexible member is supported by a support portion of the transmission shaft, and the rotation center of the rotation structure is located between the fixed portion and the support portion.
 22. The rotary guiding tool of claim 15, wherein, an end of the flexible member is mounted on a fixed portion of the support shaft, the other end of the flexible member is supported by a support portion of the transmission shaft, and the rotation center of the rotation structure is located between the fixed portion and the support portion.
 23. The rotary guiding tool of claim 11, wherein, further comprising an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.
 24. The rotary guiding tool of claim 12, wherein, further comprising an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.
 25. The rotary guiding tool of claim 13, wherein, further comprising an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.
 26. The rotary guiding tool of claim 14, wherein, further comprising an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.
 27. The rotary guiding tool of claim 15, wherein, further comprising an annular pressure balance portion connecting the inner wall of the support shaft and an outer wall of the transmission shaft, a portion of the inner wall of the support shaft, a portion of the outer wall of the transmission shaft and an inner surface of the pressure balance portion jointly define a medium cavity.
 28. The rotary guiding tool of claim 11, wherein, a shortest distance between the rotation center and the drill bit tail end is not greater than 3.5 times of a maximum radial dimension of the support shaft.
 29. A transmission device, separately connected to: a power unit having an output shaft capable of outputting a torque and an offset driving portion capable of outputting a radial force; a drill bit having a drill bit tail end; wherein, the transmission device comprises: a transmission shaft coaxially connected with the output shaft; a support shaft coaxially connected with the transmission shaft through a rotation structure, a rotation axis of the rotation structure is perpendicular to an axis of the output shaft, the support shaft has an accommodating cavity and a forward end and a rearward end formed at both ends of the accommodating cavity, a rotation center of the rotation structure is located in the accommodating cavity, and the rearward end of the support shaft is capable of being driven by the radial force output by the offset driving portion, and the forward end and the drill bit are coaxially connected to the drill bit tail end. 